Japanese Patent Laying-Open No. 63-245915 (Patent Document 1) is a prior art publication that discloses a configuration of a stationary induction apparatus including an insulating barrier. In the winding body described in Patent Document 1, an insulating sheet is provided on the inner periphery of a winding wound into a square tube, and a portion of the insulating sheet, which projects from the end of the winding, is folded outwardly and overlapped with the end of the winding. Slits extending axially are provided at least at the portions of the insulating paper which correspond to the positions of the corners of the square-tube-shaped winding, thereby forming small pieces. The bases of these small pieces are folded inwardly and then folded outwardly, thereby forming a folded insulating barrier.